Jets in Low Power Compact Radio Galaxies

Marcello GirolettiDepartment of Astronomy, University of Bologna

INAF Institute of Radio Astronomy&

G. Giovannini (UniBO, IRA)

G. B. Taylor (KAVLI, NRAO)

Outline

Parsec scale radio jets……in classical extended radio galaxies…and in compact radio sources

The Bologna Complete Sample Low Power Compact sources

New high resolution radio observationsJets, linear size, brightness, spectrum,

Doppler factor, evolution Conclusions

Parsec scale jets

parsec scale observations with VLBIshow both one- and two-sided jetsyield support for intrinsically symmetric jetsdiscover superluminal motionssuggest that parsec scale jets are relativistic

3C 66B 3C 452

Images adapted from

Giovannini et al. (2001, A

pJ)

Relativistic parsec scale jets in 19 radio galaxies

observed with VLBI (Giovannini et al. 2001) we find proper motions jet/counterjet ratios >1 large core dominance

evidence for: relativistic parsec scale

jets without distinction

between FRI and FRII now, what about compact

sources?

Bologna Complete Sample

Giovannini et al. 2005, ApJ 61895 sources selected at low frequency (from B2

and 3C surveys)no selection on core properties, thus no bias in

favour of relativistic beamingz < 0.1

81 extended radio galaxies: 65 FR I, 15 FR II, 1 FRI/II 14 compact sources: nuclei? sub-structures? intrinsic

properties (power, dimension)? evolution? young? weak? frustrated?

Mkn 421, Mkn 501 flat spectrum relativistic beaming

one sidedness superluminal motion high energy activity (optical,

X, )

poster by Giovannini et al.

Giroletti et al. 2004

Radio power vs. linear size: BL Lacs

4C 31.04 steep spectrum symmetric not beamed young radio galaxies

(Owsianik & Conway 1998) HS advancing at ~0.1 c relativistic jet knots (Taylor

et al. 2000)

Giroletti et al. 2003

Radio power vs. linear size: CSOs

Radio power vs. linear size: LLAGNLLAGN

1 pc 103 RS

Giroletti et al. 2005

NGC 4278NGC 4278 intermediate spectraintermediate spectra weak nuclear activityweak nuclear activity evidence of non thermal evidence of non thermal

emission (Nagar et al. 2002)emission (Nagar et al. 2002) relativistic jet?relativistic jet? common in “normal” nearby common in “normal” nearby

galaxygalaxy

Radio power vs. linear size: LPCLPCLow Power Compact sources: 23.9 < Log P

tot < 25.5 [W Hz-1]

1.5 < LAS < 10 [asec]

RADIO: NVSS, FIRST, some

literature (e.g. Fanti et al. 1987,

large scale); power similar to

FRIs but much smaller size

OPTICAL: ellipticals, narrow

lines, HST for e.g. 0648+27

(dust)

X-rays: few studies, low

luminosity (<1042 erg s-1)

New observations High resolution

VLA @8, 22 GHz VLBA @1.6 GHz, phase referenced (≈5 mas

resolution and ≈0.5 mJy sensitivity) Main goals:

resolve sub-kpc scale structure, e.g. jets identify core study spectral index new accurate measures for parsec scale

properties (position, flux density, …) determine intrinsic power, age, evolution…

From “blobs” to jetsAt low resolution, sources are compact, core dominated

High resolution observations reveal rich substructures, including jets, resembling

extended FRI and FRII on 10-1000 times smaller scales.

Giroletti et al. 2005, (A&A in press,

astro-ph/0506497)

0222+36

S408 = 337 mJy z = 0.03 P = 1023.9 W Hz-1

LAS = 8” Literature

kpc scale: Fanti et al. (1987)

pc scale: ???

VLA

S8 GHz = 190 mJy

S22 GHz = 90 mJy

core = 0.6

halo is resolved

two sided structure

VLBA

S1.6 GHz = 102 mJy

two sided jets

no hot spots

definitely in the plane of the sky

nicely connected to VLA maps

0258+35 S408 = 3.9 Jy z = 0.016 P = 1024.4 W Hz-1

LAS = 4” Literature

kpc scale: Fanti et al. (1987)

pc scale: compact, with flux density excess on short spacings

VLA

S8 GHz = 620 mJy

S22 GHz = 270 mJy

symmetric FRI-like, but LS ~ 5 kpc

two knots in jet

zero hot spot

VLBAphase-ref essential

Score = 7 mJy

Sblob = 240 mJy

one-sided

jet/blob/shock/more?

0648+27 S408 = 0.27 Jy z = 0.04 P = 1024.0 W Hz-1

LAS = 1.5” Literature

kpc scale: Morganti et al. (2003), large amount of HI

VLBAphase-ref provides:

1. DETECTION (Score = 4 mJy)

2. POSITION

3. tentative JET

VLAS8 GHz = (19 + 14) mJy

S22 GHz = 10 mJy

symmetric double at 8 GHz…

…resolved with compact core at 22 GHz!

NO HS!

1037+30VLA 8 GHzSc = 2.7 mJy

VLA 22 GHzSc = 1.3 mJy

VLBA 1.6 GHzB = 2.3 mJy/beam

VLA 1.4 GHzVLA 8 GHzSc = 2.7 mJy

VLA 22 GHzSc = 1.3 mJy

VLBA 1.6 GHzB = 2.3 mJy/beam

VLA 1.4 GHz S408 = 1.1 Jy z = 0.09 P = 1025.4 W Hz-1

LAS = 3” Literature

kpc scale: Fanti et al. (1987)

pc scale: not detected

New results two-sided, with jets

and hot spot Tkin = 4.5 x 104 yr

Jets in LPCs

LPCs reveal rich, complex structures at high resolutionlobes, hot spots, fed by jets

radio power typical of FR Is suggests relativistic regimes0222+36: > 0.6, ~ 85°0258+35: > 0.9, 40° < < 50°

jets typically <1 kpc long structure is often two-sided

Radio spectra

One more piece of information…

little contamination from core

Beq ~ 102 G Tsyn ~ 105-106 yr vadv, syn << c

consistent with slow/ceased advance in the external medium

Why are these sources compact, then? no beaming no projection one source with hot spots youth many sources without hot spots

frustration, low power jets, short lived one source with worthless core dying,

intermittentwill young sources ever grow to kiloparsec

scale size?

Summary 5 low power compact radio sources

power similar to FR I but size < 1 kpc high frequency VLA observations

resolved structures well identified cores two-sided, one source with hot spots

phase ref. VLBA observations 4/5 detections 3/5 detections of parsec scale jets

main observational results objects on the plane of the sky (two-sidedness, low core

dominance) intrinsically small radiative ages about 105 – 106 yrs

Conclusions Reasons of compactness

1. youth2. frustration or short lived activity3. intermittent nucleus4. (projection)

Different physical state powerful jets with Doppler beaming vs low kinematic

power jets lack of hot spots: end of interaction? end of growth?

short lived sources? transition to radio quiet and non active nuclei

Samples as the BCS are important to understand these differences need to be completed to the faintest sources

0222+36, spectrum of components

Freq. (GHz)

Halo

(mJy)Lobes (mJy)

Core (mJy)

0.325 188 191 0.9

0.365 174 177 1.2

0.408 170 165 1.8

1.4 36 52 102

5.0 8 36 180

8.4 <1 26 166

22.5 <1 6 90

VLA archival data reanalyzed:

B configuration, 5 GHz

CORE

self = 3.3 GHz

B = 50 mG

LOBES

br = 9 GHz

Beq = 130 G

Tsyn = 4 x 105 yr

HALO

br = 300 MHz

Beq = 7 G

Tsyn = 1.3 x 108 yr

0222+36, age of components

0258+35: spectrum and age good coverage between 74 MHz and 22 GHz little contamination from core Beq = 90 G

Tsyn = 7 x 105 yr

vadv, syn = 0.005 c

0648+27: spectrum and age some literature data at low freq. dominant core Beq = 95 G

Tsyn = 3.5 x 105 yr large uncertainty